SS4 



PROCKKOINOS OP THB 



sulphuric ncid. The fornuT exists in the soil in combination 

 with various bases coiisiiiutinir sulphates ; the latter is generated 

 during the decay or putrefaction of many organic substances, and 

 is conse<iuently present in manure ; it is also present in very 

 minute (juantily in the air. 'J he formation of this gas in manures, 

 N:c. dcjK'nds on the fai t that sulpliates. or salts of sulphuric acid, 

 are liable to be decomp<»sed by decaying organic matters, and 

 hence those animal and vegetable substances which contain sul- 

 phates, frequently evolve sulphuretted hydrogen when they 

 decay. In such cases the presence of this gas is known by its 

 exceiMlingly offensive odour, and we are therefore warned of its 

 presence and enabled to guard against the bad effects which it 

 might produce, for it is one of the most poisonous gases known : 

 a very small quantity of it in the air producing bad effects on 

 those who respire it, and in larger quantities proving fatal. The 

 influence exerted by this gas on the animal economy is tolerably 

 well known from the experiments of Thenard and Dupuytien, 

 who exposed different animals to atmospheres contaminated with 

 various j)roportions of this gas, and the effect produced by a small 

 quantity in the air on the human frame is very well known to 

 chemists and physiologists. 1 he action however which sul- 

 phuretted hydrogen and its compounds have on growing plants 

 is almost wholly unknown. It is commonly believed from the 

 few experiments which have been published on this subject, such 

 as those of Christison and Turner, that sulphuretted hydrogen 

 gas possesses as poisonous properties with regard to plants, as it 

 does with respect to animals. I will not now bring forward the 

 written opinions published on this subject, but merely quote a 

 passage from the writings of Liebig. Speaking of the refuse 

 ammoniacal liquor of the gas works, a fluid which always contains 

 a small quantity of sulphuretted hydrogen, he says " Now the 

 " ammoniacal liquor of the gas works contains the ammonia in 

 " the form of carbonate and bydrosulphate (sulphuret of ammo- 

 " nium). The latter compound is a deadly poison to vegetables, 

 nor can we conceive that by dilution its properties can be 

 ** changed." This statement of Liebig is probably in part founded 

 on the known effects of the gas upon animals, and partly on the 

 fact that farmers in the preparation of manures, always expose it 

 in a heap for some time until the greater part of the sulphuretted 

 hydrogen is dissipated. In the course of experiments, I was 

 leid to make trial of the action of some of the compounds of 

 this gas on growing vegetables, and the results I obtained were 

 very different from what I had expected. I made use of the 

 hydrosulphuret of ammonia, the very compound described by 

 Liebig as being a ** deadly poison but in place of killing plants 



